96 



THE LIAS AMMONITES. 



Pholadomya ambigua, Sow. 

 Pleuromya granata, Simp. 



— concinna, Goldf. 



— costata, Young and 



— ovata, Rom. 

 Cardinia crassissima, Sow. 

 Gonioinya capricorni, Wrt. 

 Cucullaea Munsteri, Ziet. 

 Gresslya intermedia, Simp. 

 Cypricardia cucuUata, Miinst. 

 Modiola scalprum, Sow. 

 Limea acuticosta, Goldf. 

 Monotis insequivalvis, Sow. 



Terebratula punctata, Sow. 

 Waldiieimia resupinata. Sow. 



— cornuta, Sow. 



— Edwardsii, David. 



Cidaris Edwardsii, Wrt. 

 Hemipedina Jardinii, Wrt. 

 Ophioderma Milleri. 



Lamellibranchiata. 



Ceromya liueata, Will 

 Arcomya elongata, Rom. 

 Unicardium cardioides, Phil. 

 Bird. Protocardium triincatum, Phil. 



Cardinia crassiuscula, Sow. 

 Lima Hermanni, Voltz. 



— duplicata, Sow. 



— pectinoides, Sow. 

 Pecten calvus, Goldf. 



— aequivalvis, Sow. 



— Innularis, Rum. 

 Gryphsea cymbium, Lamk. 

 Ostrea margaritacea, Wrt. 



Brachiopoda. 



Rhynchonella tetraedra, Sow. 



• — variabilis, Schloth. 



— acuta, Sow. 



Lingula Beanii, Phil. 



Echinodermata. 



Ophiolepis Murravi, Wright. 

 Extracrinus subangularis, Mill. 

 Pentacrinus gracilis, Charlesworth. 



The Marlstone attains a great development in Yorkshire, and is fully exposed in 

 the coast sections near Staithes, Colborn Nab, and Boulby. " The sandy, conchiferous 

 marlstone beds," says Prof. Phillips,^ " which in Colborn Nab cover the Lower Lias 

 shale, are seen rising with it and contributing to swell the altitude of Boulby and Rock- 

 clifF. The lower part of this series is generally the most solid, and projects in broad, 

 compact floors above the Lias. On the surfaces of such beds lie innumerable multitudes 

 of Oysters, Dentalia, Pectens, Protocardium truncatum, Monotis incequivalvis, and more 

 rarely, about Staithes, beautiful fossil Star-fishes of the genus Ophioderma.'^ In Boulby 

 Cliffs'^ the ironstone and Marlstone series consist of — 



a. The ironstone bands, which are numerous layers of firmly connected nodules 

 of ironstone, often septariate, and enclosing coniferous wood, Pectines, Aviculse, 

 Terebratulse, and from twenty to forty feet thick. 



b. The Marlstone series, consisting of alternations of sandy Lias shale and sandstones, 

 which are frequently calcareous, and generally full of shells. The lower beds are usually 

 more solid, and project from the chffs in broad floors, covered with Pectens, Cardia, 

 Dentalia, Aviculse, Gryphsese, &c. The thickness variable from forty to 120 feet. 



The molluscan fauna of these beds closely resembles the list already given from the 

 Marlstone of Gloucestershire. Among the Echinodermata, however, are found species 

 ' ' Geology of Yorkshire,' p. 101. » Ibid., p. 102. 



